Certain known wind power turbines are described in the following patent documents: WO 2008/078342 A1; EP 1,363,019 A2; DE 196 52 673 A1; DE 38 44 505 A1; ES 2,140,301 A2; EP 1,589,222 A2; DE 297 06 98011; and FR 2,810,374 A1.
One known high-power wind power turbine is described in the FIG. 1, 4, 5, 6, 9, 11, 12, 13, 16, 17 embodiments of WO 2008/078342. In this PCT patent application, the wind power turbine comprises at least two electric machines on opposite sides of the supporting structure.
The technical solutions of certain known wind power turbines provide for balanced mass distribution with respect to the supporting structure, and for extremely easy assembly, but the transmission assembly between the first and second electric machine poses other problems. For example, any oscillation of the first rotor is amplified in the second. More specifically, the first rotor being connected directly to the blade assembly, wind action on the blade assembly may result in displacement of the first rotor, substantially in the form of a slight variation in the concentricity of the first rotor and first stator and/or in the slope of the first axis, which are considered acceptable within a given range. A variation in the slope of the first axis displaces the second rotor in direct proportion to the distance between the first and second rotor, and may possibly result in displacement of the second rotor that is no longer acceptable. Generally speaking, displacement of the first and second rotor is considered unacceptable when it reduces the air gap to such an extent as to impair operation of the first and/or second electric machine, or when it reduces the working life of parts of the first and/or second electric machine supporting the first and/or second rotor respectively. Displacement could be limited by supporting the first and second rotor using hyperstatic systems. This solution, however, would increase the weight and complicate the design of the wind power turbine, would limit access to the active parts of the first and second electric machine, and would increase stress and wear.
Another technical problem for certain known wind power turbines is the high degree of precision involved in manufacturing and assembling the component parts of the first and second electric machine to ensure optimum performance of the wind power turbine (i.e., performance ensuring maximum efficiency of the first and second electric machine in relation to wear). In other words: the active parts of the first and second rotor must be positioned completely facing the active parts of the first and second stator respectively; and the first and second stator must have coincident axes of symmetry, and the first and second axis must be coincident.
Even only minor dimensional differences in the fabrication or assembly of the first and second electric machine could result in asymmetry or misalignment, and therefore impaired operation, of the first and second electric machine.
Additionally, differences in thermal expansion in the first and second electric machine and in the transmission assembly pose another technical problem for certain known wind power turbines. That is, the first and second electric machine comprise metal structures made of different materials and subject, by position and function, to different degrees of overheating. And, in actual use, differences in thermal expansion may result in asymmetry or misalignment of parts of the first and second electric machine, and in the transmission assembly.